1. Field of the Invention
The present invention generally relates to brake control systems for railroad locomotives and, more particularly, to a system for controlling the brakes of a helper locomotive from a lead locomotive in a train.
2. Description of the Prior Art
End of Train (EOT) signalling and monitoring equipment is now widely used, in place of cabooses, to meet operating and safety requirements of railroads. The information monitored by the EOT unit typically includes the air pressure of the brake line, battery condition, marker light operation, and train movement. This information is transmitted to the crew in the locomotive by a battery powered telemetry transmitter. In addition, the EOT unit typically includes a marker light mounted a specific height above the track and having a well defined beam pattern.
The EOT unit is mounted on the coupler of the last car of the train, and specific coupler mounts have been designed to allow a switching engine or a helper locomotive to couple to the last train without damaging the EOT unit. While not necessary for a switching engine in a rail yard, it is important for a helper locomotive to provide braking for the train. The braking provided by the helper locomotive should be controlled by the engineman in the lead locomotive while the helper locomotive is coupled to the train. To better understand the problem, consider a typical application of a helper locomotive for, say, a train transporting coal from mines in a mountainous region to a port for shipment to an ultimate destination. Such trains may be a mile long, and the consist may comprise three locomotives connected in tandem at the head of the train. The power provided by the three locomotives are more than adequate for the run from the mountains to the port, and quite often a helper locomotive is attached at the beginning of the run to clear the mountains. Once clear of the mountains, the helper locomotive is disconnected and returns to its point of origin.
The air brake system of the train comprises a brake pipe which extends the length of the train. The pressure is maintained in the brake pipe by the lead locomotive except when the engineman in the lead locomotive applies the brakes by releasing air pressure. The drop in air pressure propagates down the brake pipe causing brakes to be applied by the locomotives and all the cars in the train. With the advent of two-way EOT units, an emergency braking event can be initiated by the engineman by causing air pressure to be vented simultaneously at the front and back of the train.
Currently, the brake pipe hose of helper locomotives is connected to the train, as required by Federal Railroad Administration (FRA) Rule 232.15. This makes the brakes of the helper locomotive(s) respond like any other car in the train, thus giving control of the brakes to the engineer in the lead locomotive. Coupling and uncoupling of the brake hose of the helper locomotive to the train is accomplished manually. Both operations expose railroad personnel to risk of serious injury. Therefore, a safer alternative needs to be found to the manual coupling and uncoupling of the brake hose of the helper locomotive to the train.
One approach, exemplified in U.S. Pat. No. 5,180,213 to Kingsbury, is to provide a special valve that allows the brake pipe of the train to be coupled to the that of the helper locomotive without a loss of air in the brake pipe on initial coupling and upon decoupling. This valve allows an air tight coupling to the brake pipe hose at the end of the train before a pneumatic communication is established with the brake pipe of the helper locomotive. This coupling, however, still must be accomplished manually at the time the helper locomotive is coupled to the train. On the other hand, the design is such that when the helper locomotive decouples, the brake hose coupling has a break-away connection that prevents any loss of air pressure in the brake pipe of the train, allowing an on-the-fly decoupling of the helper locomotive.
While the Kingsbury approach accomplishes the stated goals of allowing the engineman in the lead locomotive to control the brakes of the helper locomotive as long as the helper locomotive is coupled to the train, it has several significant drawbacks. First, it requires that someone manually make the brake pipe connection causing delay but, more importantly, exposing the person making the connection to some considerable danger. And second, the valve mechanism remains on the train. This is less than ideal from the point of view of the logistics and reliability of the mechanism. Having the mechanism ride with the train exposes the train to an added potential problem due either to equipment malfunction or equipment theft and vandalism. Also, sometime, somewhere the valve mechanism must be removed from the train and shipped back to the helper location--a logistical nightmare for the railroads.